/*
 * Licensed to the Apache Software Foundation (ASF) under one
 * or more contributor license agreements.  See the NOTICE file
 * distributed with this work for additional information
 * regarding copyright ownership.  The ASF licenses this file
 * to you under the Apache License, Version 2.0 (the
 * "License"); you may not use this file except in compliance
 * with the License.  You may obtain a copy of the License at
 *
 *     http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing,
 * software distributed under the License is distributed on an
 * "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY
 * KIND, either express or implied.  See the License for the
 * specific language governing permissions and limitations
 * under the License.
 */

package org.apache.iotdb.db.utils.datastructure;

import com.google.common.collect.MinMaxPriorityQueue;

import java.util.Comparator;
import java.util.List;
import java.util.concurrent.CopyOnWriteArrayList;
import java.util.concurrent.locks.Condition;
import java.util.concurrent.locks.ReentrantLock;

/**
 * This is a priority blocking queue with a maximum size. If the queue's size is larger than the max
 * size, the element with max priority will be kick out.
 */
public class FixedPriorityBlockingQueue<T> {
    private int maxSize;
    private Comparator<T> comparator;
    private MinMaxPriorityQueue<T> queue;

    private ReentrantLock lock = new ReentrantLock();
    private Condition notEmpty = lock.newCondition();

    private List<PollLastHook> pollLastHookList = new CopyOnWriteArrayList<>();

    public FixedPriorityBlockingQueue(int maxSize, Comparator<T> comparator) {
        this.maxSize = maxSize;
        this.comparator = comparator;
        this.queue = MinMaxPriorityQueue.orderedBy(comparator).maximumSize(maxSize + 1).create();
    }

    public void put(T element) throws InterruptedException {
        final ReentrantLock lock = this.lock;
        lock.lockInterruptibly();
        try {
            queue.add(element);
            if (queue.size() > maxSize) {
                this.pollLast();
            }
            notEmpty.signal();
        } finally {
            lock.unlock();
        }
    }

    /**
     * Return the element with min priority. If the queue is empty, the thread will be blocked util
     * there are some elements inserted into the queue.
     *
     * @return
     * @throws InterruptedException
     */
    public T take() throws InterruptedException {
        final ReentrantLock lock = this.lock;
        lock.lockInterruptibly();
        try {
            while (queue.size() == 0) {
                notEmpty.await();
            }
            return queue.pollFirst();
        } finally {
            this.lock.unlock();
        }
    }

    /**
     * Return the element with max priority. If the queue is empty, the thread will be blocked util
     * there are some elements inserted into the queue.
     *
     * @return
     * @throws InterruptedException
     */
    public T takeMax() throws InterruptedException {
        final ReentrantLock lock = this.lock;
        lock.lockInterruptibly();
        try {
            while (queue.size() == 0) {
                notEmpty.await();
            }
            return queue.pollLast();
        } finally {
            this.lock.unlock();
        }
    }

    /**
     * Add a hook for this queue. If an element is kicked out because the queue's size exceed the
     * largest value, the hook will apply to this element. Notice, multiple hooks can be added to a
     * queue, and all of them will be applied to the element kicked out. The order in which they are
     * applied depends on the order in which they were registered.
     *
     * @param hook
     */
    public void regsitPollLastHook(PollLastHook<T> hook) {
        this.pollLastHookList.add(hook);
    }

    public boolean contains(T element) {
        final ReentrantLock lock = this.lock;
        lock.lock();
        try {
            return queue.contains(element);
        } finally {
            lock.unlock();
        }
    }

    public int size() {
        final ReentrantLock lock = this.lock;
        lock.lock();
        try {
            return queue.size();
        } finally {
            lock.unlock();
        }
    }

    public void clear() {
        final ReentrantLock lock = this.lock;
        lock.lock();
        try {
            while (queue.size() != 0) {
                this.pollLast();
            }
        } finally {
            lock.unlock();
        }
    }

    public boolean isEmpty() {
        final ReentrantLock lock = this.lock;
        lock.lock();
        try {
            return queue.isEmpty();
        } finally {
            lock.unlock();
        }
    }

    private void pollLast() {
        final ReentrantLock lock = this.lock;
        lock.lock();
        T element = null;
        try {
            element = queue.pollLast();
        } finally {
            lock.unlock();
        }
        if (element != null) {
            T finalElement = element;
            pollLastHookList.forEach(x -> x.apply(finalElement));
        }
    }

    public Comparator<T> getComparator() {
        return this.comparator;
    }

    public int getMaxSize() {
        return this.maxSize;
    }

    @FunctionalInterface
    public interface PollLastHook<T> {
        void apply(T x);
    }

    @Override
    public String toString() {
        return queue.toString();
    }
}
